PdBio midterm 2 Flashcards
(114 cards)
1
Q
molecule
A
2+ atoms held together b y various forces or bonds
2
Q
Types of bonding
A
covalent, ionic, hydrogen
3
Q
covalent bonds
A
sharing of electrons between 2 nonmetal atoms
4
Q
ionic bonds
A
transferring electrons between metal and nonmetal atoms (ex: NaCl)
5
Q
hydrogen bonds
A
H partial positive charge bonding with an electronegative atom such as N, O, or F
6
Q
4 types of macromolecules
A
carbohydrates, lipids, proteins, nucleic acids
7
Q
monomers
A
many small molecules linked together to form polymers
monomer: simple subunit (mono=1)
polymer: longer chain (poly=many)
8
Q
polymer formation done by…
A
dehydration
9
Q
dehydration
A
removes a water molecule (needs energy/enzymes to help)
10
Q
polymer breakdown done by…
A
hydrolysis
11
Q
hydrolysis
A
water added back in each time a monomer is released (enzyme used to catalyze the breakdown)
12
Q
Carbohydrates
- monomer?
- function?
- composition?
- bonds used:
A
- monomer = monosaccharide sugar subunit
- function: store energy & aid in cell recognition
- composition: C,H,O atoms
- bonds used: covalent
13
Q
Lipids -monomer? -function? -composition? bonds used:
A
- monomer = glycerol & fatty acids
- function: store energy & add structure/protection
- composition: C & H atoms, clumped together
- bonds used: covalent no H bonds
14
Q
Which macromolecule is non polar and insoluble in H2O?
A
Lipids
15
Q
Proteins -monomer? -function? composition? bonds used:
A
- monomer = amino acids
- function: provide structure & communicate
- composition: C,H,O,N,S atoms
- 20 different amino acids with a different R group
- changing R group also changes pH and charge
-bonds used: depends on the structure
16
Q
What does the R group of an amino acid determine
A
chemical characteristics > pH and charge
17
Q
Nucleic Acids
- monomer?
- function?
- composition?
- bonds used?
A
- monomer = nucleotide
- function: storage, expression, transmission of genetic info
- composition: phosphate group, 5C sugar, and a base (C,U,T,A,G)
- bonds used: covalent & hydrogen
18
Q
purines in DNA
A
Adenine (A) and Guanine (G)
19
Q
pyrimidines in DNA
A
Cytosine (C) and Thymine (T)
20
Q
Base pairs in DNA - which bases pair with each other?
A
A&T pair together
C&G pair together
21
Q
Things to remember about DNA structure (3)
A
base pairing (ATCG) double helix - anti-parallel no hydroxyl group on 2'
22
Q
purines in RNA
A
Adenine (A) and Guanine (G)
23
Q
pyrimidines in RNA
A
Cytosine (C) and Uracil (U)
24
Q
Base pairs in RNA - which bases pair with each other?
A
A & U pair together
C & G pair together
25
Things to remember about RNA structure (3)
base pairing (AUCG)
single strand
hydroxyl group on 2'
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DNA stands for
Deoxyribonucleic Acid
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RNA stands for
Ribonucleic Acid
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General process of the Central Dogma
DNA transcribed to RNA translated to Proteins
29
Why is DNA replication necessary?
It is necessary because cells divide and they need double the amount of DNA so the resulting daughter cells will contain the correct amount of DNA
30
Types of DNA replication (3)
1. conservative
2. *semi-conservative*
3. dispersive replication
31
What is the most common/popular type of replication? Explain it.
Semi-conservative = DNA replication produces DNA molecules with 1 parental strand and 1 newly made daughter strand
32
Where does replication begin?
Origin of replication - provides an opening called a replication bubble that forms two replication forks
33
How many origins of replication are found in eukaryotes and prokaryotes?
- eukaryotes may have multiple origins of replication
| - prokaryotes (bacteria) only have 1 origin of replication
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Where does DNA replication happen in a cell and in which way does it proceed?
DNA replication happens in the nucleus. It proceeds outward from the forks.
35
What is the direction of DNA replication?
5' to 3' direction in the primary structure of nucleic acids
36
What is the composition of nucleic acids (in more detail)?
- the 5' end has the free phosphate attached to the 5' carbon
- the 3' end has an OH group attached to the 3' carbon
- 2' end has either (H) for DNA or (OH) for RNA
- Nitrogen base attached to 1'C on sugar (ATCG)
- nucleic acids are sequenced from 5' to 3'
37
Directions of the leading and lagging strands?
- leading strand is moving TOWARD the replication fork in 5' to 3' direction
- lagging strand is moving AWAY from the replication fork in 5' to 3' direction
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Players in DNA replication (7)
- helicase
- single strand binding proteins (SSBP)
- topoisomerase
- primase
- DNA polymerase III
- DNA polymerase I
- Ligase
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Function of helicase
"unzips" DNA strands
40
Function f single strand binding protein (SSBP)
keeps the strands separated
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Function of topoisomerase
loosens the tension to prevent supercoiling in the rest of the DNA strand
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Function of primase
makes RNA primer so that the enzymes know where to start building
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Function of DNA polymerase III
builds the new base (5' to 3')
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Function of DNA polymerase I
removes RNA primers (Okazaki fragments)
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Function of ligase
links the bases together
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DNA replication accuracy based off of 3 things
1) Hydrogen bonding between A & T and between G & C is more stable than mismatched combinations
2) Active site of DNA polymerase is unlikely to form bonds if pairs are mismatched
3) DNA polymerase can proofread to remove mismatched pairs (DNA polymerase backs up and digests linkages)
47
DNA replication accuracy based off of 3 things
1) Hydrogen bonding between A & T and between G & C is more stable than mismatched combinations
2) Active site of DNA polymerase is unlikely to form bonds if pairs are mismatched
3) DNA polymerase can proofread to remove mismatched pairs (DNA polymerase backs up and digests linkages)
48
Griffith experiment
experiment with rough/smooth strains of streptococcus and mice
-process of "heat killing" bacteria denatures the proteins, but DNA is still intact
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Hershey-Chase
experiment - infection, blending, centrifuge (heavy bacteria pellets at bottom)
-conclusion: DNA was injected into bacteria, not protein. DNA is the genetic material
50
Beadle & Tatum
Hypothesize one gene codes for one enzyme/protein
| -mutated the DNA one enzyme at a time
51
Variations/exceptions to the Central Dogma
- the genetic code is not really universal
| - mitochondria usually have their own genetic code different from the code that governs the nuclear genome.
52
What bonds link amino acids together in proteins?
peptide bonds
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In what direction are amino acids built?
N - C direction
54
What is polymerization and what does it require?
the binding together of monomers
| -requires 1+ enzymes and energy to form
55
What are the 4 levels of structure in proteins (describe)?
1. primary: the sequence of amino acids (covalent peptide bonds) form a linear string of peptide bonds in the N to C direction
2. secondary: hydrogen bonds form alpha helices and beta pleated sheets (2 STRUCTURES HERE)
3. tertiary: secondary structures and other regions fold into 3D shapes to become functional (all kinds of bonds)
4. quaternary: two or more polypeptides join together to form a functional protein (all kinds of bonds)
56
What are the two classes of nucleic acids?
DNA (stores genetic info encoded in the sequence of nucleotide monomers)
RNA (decodes DNA into instructions for linking together a specific sequence of amino acids)
57
How can you tell if a nucleic acid has DNA or RNA?
look at the 2' carbon
- if hydrogen (H) is present it is DNA
- if oxygen (OH) is present it is RNA
58
What is an element found in all organic molecules?
Carbon
59
Meselson & Stahl
Proved that DNA replication occurs through semi-conservative replication
60
DNA has to be made in the _______ direction so you must add to the _____ end every time.
DNA has to be made in the 5' to 3' direction so you must add to the 3' end every time
61
What is the difference between purines and pyrimidines?
Purines have a double ring structure and pyrimidines have a single ring structure
62
The double helix structure of DNA was proposed by who?
Watson and Crick
63
The ability to predict the DNA sequence in one strand based on the sequence of another strand is referred to as what?
complementarity
64
During DNA replication, the lagging strand is synthesized as a series of small fragments called
Okazaki fragments
65
A DNA polymerase can detect a mismatched nucleotide and remove it from the daughter strand. It does so by digesting the linkages in the 3' to 5' direction to remove the incorrect base and then changing direction to synthesize again in the 5' to 3' direction. This process is called...?
Proofreading
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Synthesis is ______
bidirectional
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Helices breaks _____ bonds between nucleotides to open the replication fork
hydrogen
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synthesis of the leading strand - direction and process?
synthesizes in the 5' to 3' direction TOWARD the replication fork.
The DNA polymerase III recognizes the location of the primer sequence and clamps hold of the DNA at that location. It then creates a copy of the leading strand as it travels toward the replication fork.
69
synthesis of the lagging strand - direction and process?
synthesis in the 5' to 3' direction AWAY from the replication fork.
DNA polymerase III would synthesize short fragments (Okazaki fragments) of DNA along the lagging strand that later are linked together to form a continuous strand of DNA. DNA polymerase I comes in and removes the RNA primer and synthesizes DNA in its place. DNA ligase joins the Okazaki fragment with a phosphodiester bond.
70
Where does RNA transcription occur in prokaryotes and eukaryotes?
In the cytoplasm in prokaryotes and the nucleus in eukaryotes
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The mRNA strand that is synthesized with a DNA strand serving as a template is referred to as ______ to the DNA strand.
complementary
72
example of DNA template strand sequence to mRNA sequence:
| GAATCT >>>
CUUAGA
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Which strand of DNA serves as the template for mRNA?
The 3' to 5' strand
- non-coding strand
- template strand
74
Which strand of DNA does NOT serve as the template for mRNA?
The 5' to 3' strand
- coding strand
- the gene
- non-template strand
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In which direction does mRNA synthesize?
5' to 3' direction
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Which enzyme transcribes the template strand of DNA to mRNA?
RNA polymerase
77
Steps of transcription
Initiation
-Sigma, a protein subunit, must bind to the DNA
Elongation
-Sigma and RNA polymerase together form a holoenzyme
-The sigma guides the RNA polymerase to specific PROMOTER sequences on the DNA template strand
78
What is a holoenzyme and what creates it?
A holoenzyme is an enzyme made up of core enzymes and other required proteins
It's created by a sigma and RNA polymerase
79
How to know if it is a bacterial promoter?
- 10 box: 10 bases upstream during transcription is the sequence TATAAT
- 35 box: consisting of the sequence TTGACA is 35 bases upstream
* all bacterial promotes have a -10 box and a -35 box
80
How to know if it is a eukaryotic promoter?
- more complex series of promoters than prokaryotes
| - many eukaryotic promoters include a unique sequence called the TATA box centered about 30 base pairs upstream
81
RNA processing in eukaryotes
- introns
- exons
- snRNPs ("snurps")
- capping
- poly A tail
82
What are introns?
intervening noncoding sequences transcribed but not translated
83
What are exons?
exons are coding regions of eukaryotic genes that are found in mature mRNA
84
What is required to make a functional mRNA?
the introns (noncoding regions) must be removed through splicing
85
What is the removal of introns called and what enzyme carries out this function?
Splicing.
snRNPs ("snurps") remove the introns
-look at notes for pictures
86
What is capping?
a cap is added to the 5' end of the mRNA (called 5' cap)
| -necessary for mRNA to exit nucleus and prevent degradation
87
What is the poly A tail?
many A in sequence added to the 3' end (called poly A tail)
- aids in the export mRNA from nucleus
- increases stability and lifespan
88
Where does RNA translation occur?
translation happens in ribosomes in the cytosol or rough ER
89
If a codon in a strand of mRNA is UCG (5' to 3' direction), what is the anticodon?
AGC (3' to 5') direction
90
What does tRNA do?
carries the amino acid.
| -the anticodon part of the tRNA molecule allows binding between the tRNA and mRNA codon
91
What is aminoacyl-tRNA synthetase?
catalyzes attachment of amino acids to tRNA (one for each of 20 different amino acids)
-results in tRNA with amino acid attached
92
When is the tRNA charged?
When it carries an amino acid
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Ribosomes can be separated into two subunits:
1. the small subunit - holds the mRNA in place during translation
2. the large subunit - where peptide bonds form
94
During translation ___ tRNAs line up within the ribosome.
3
95
Process of translation (general)
1. initiation - mRNA binds to small subunit off ribosome in 5' to 3' direction
- ribosome looks for AUG start codon (anticodon UAC)
- large subunit of ribosome binds
- peptide bond formation
- continues until stop codon
- polypeptide relaxed with release factors and mRNA chain released and ribosome breaks apart
96
What allows the polypeptide to be released?
release factors
97
What is the function of telomerase?
makes extra DNA on 3' overhangs
98
What is the function of the sigma in transcription?
Searches for the promoters
99
What are the promoters?
sequence of DNA
in prokaryotes -35 and -10 boxes
in eukaryotes TATA
100
What is the terminator?
Sequence of DNA that indicates the finish of transcription
101
What does the splicosome do?
w/ snRNPs that cuts out introns and it adds a cap to the 5' end and a poly A tail to the 3' end
102
Players in Transcription? (5)
- sigma
- promoter
- RNA polymerase
- terminator sequence
- splicosome
103
Players in translation?
- codon on mRNA 5' to 3'
- anticodon on tRNA 3' to 5'
- tRNA synthetase
- look for AUG start codon
- until stop codon
104
What is the start codon?
AUG
105
3 Stages of transcription?
initiation, elongation, termination
106
Transcription results in...
1) mRNA that encodes a polypeptide
2) rRNA that'll be incorporated in a ribosome
3) tRNA that'll be used to translate an mRNA
107
Transcription units are called _____
genes
108
In transcription in eukaryotes, ______ are used instead off the sigma protein that is used during transcription in prokaryotes
transcription factors that detect recognition sites in the eukaryotic promoter regions
binds too the TATA box at -30
109
What are the 3 different kinds of RNA polymerases?
I: makes large rRNA transcripts
II: makes mRNA transcripts
III: makes tRNA and small rRNA transcripts
110
Why does the final product of transcription result in mRNA that is different in length from the original gene sequence? (2)
1) Because of splicing and introns being taken out by snRNPs and only exons staying.
2) The addition of the 5' cap and the 3' poly A tail
111
In ______, the mRNA must be completely transcribed and processed before it leaves the nucleus to be translated by the ribosome machinery
eukaryotes
112
3 steps of translation?
1) initiation
- the mRNA has a ribosome-winding site and initiation factors to help temporarily bind the mRNA to the small ribosomal subunit. This allows aminoacyl tRNA to bind to the start codon which allows the large ribosomal subunit to bind to the RNA complex
2) elongation
- appropriate aminoacyl tRNAs bind to specific locations in the mRNA complex which initiates movement of the tRNAs in the active sites and movement of ribosome along the mRNA so that the A-site becomes open for the next appropriate aminoacyl tRNA
- growing polypeptide attached to the tRNA in the P-site and the go methionine residues detached from the tRNA that's still attached to the start codon in the E-site
3) termination
- a tRNA that lacks an amino acid comes to occupy the A-site and is complimentary to the termination codon
- the last amino acids in the chain detach from their respective tRNAs, the polypeptide has nothing holding it in place, so it detaches from the ribosomal complex
- mRNA is now free to combine with another ribosome and produce more polypeptide products
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An tRNA is ______ when an amino acid is attached by the aminoacyl-tRNA synthetase
charged
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Ribosomes contain ____ and _____.
protetins
| rRNA
